According to Fraunhofer, HD-AAC offers better-quality than CDs, in smaller file sizes... I currently maintain a massive (by consumer standards) music collection in 320kbs, however due to storage limitations, we're about to buy a second NAS (network attached atorage) server with lots and lots of storage that will be used exclusively for music (the current NAS server shares all our data) and I want to re-rip all of my CDs into something much better quality.

Extensive research has shown that in theory, HD-AAC is the best choice because it is backwards-compatible with AAC and natively supports full metadata - I was considering FLAC a while back, but I had a few problems with the metadata and album artwork...

Anyway, I seem to be turning a simple question into an essay, so I'll leave it at that - how do I rip CDs into HD-AAC?

My understanding is that HD-AAC is hybrid lossless/lossy. The "better than CD" quality claim is related to support for 24 bit / 192 kHz sampling, but that won't improve quality when ripping CDs, the ripped files will remain 16 bit / 44.1 kHz. The advantage over FLAC (if I got this right) is that AAC-aware players will be able to play the lossy part even if they don't support HD-AAC.

In order to rip to HD-AAC, you need to find a command-line encoder (do they sell one?) and set up a custom command line in the "encoder" field of your ripper of choice (EAC or whatever).